The present invention relates to an image forming apparatus, a printing method and a control program, and specifically relates to an image forming apparatus, a printing method and a control program, each of which prints a document created on the basis of the XML Paper Specification (hereinafter, also referred to as the XPS).
In recent years, there have been increasingly proliferated in the market various kinds of copiers or multi-functional apparatuses, each provided with a combination of plural functions, such as a copy function, a facsimile function, a printer function, a scanner function, etc., (hereinafter, referred to as an image forming apparatus as a general term for each of them). When the image forming apparatus is employed as the network printer to implement the printing operation, at first, the concerned document is created by using the application program installed in advance in the computer terminal device coupled to the network, and then, the created document is converted to the print data in the format of the Page Description Language (hereinafter, also referred to as the PDL, for simplicity), so as to be transmitted to the image forming apparatus concerned. Receiving the print data from the computer terminal device, the image forming apparatus parses the print data to create intermediate data, and then, further converts the intermediate data to bitmap data, so as to output an image based on the bitmap data onto a paper medium.
On that occasion, since there is a fear that the print data to be transmitted through the network might be possibly falsified during the transmitting operation of the print data, the method for judging the validity of the print data by employing a digital signature has been usually employed. For instance, Japanese Non-Examined Patent Publication Tokkai 2005-267022 sets forth a method in which: the digital signature and the electronic certificate attached to the document data concerned are used to decrypt the digital signature by employing the public key included in the electronic certificate to acquire hash values; the hash values inherent to the document data are compared with the hash values acquired; the document data is determined to not to be falsified if the hash values inherent to the document data coincide with those acquired; document data including hidden character information is created to output to the printer concerned; and thus the printer prints an image represented by the document data including the hidden character information.
Accordingly, by employing the digital signature mentioned in the above, it is possible to judge presence or absence of a manipulation of the print data. Further, when the manipulation of the print data is detected, the conventional image forming apparatus has implemented the printing operation in any one of three modes including a first mode in which all of the documents are printed irrespective of the validity of the digital signature, a second mode in which all of the documents are printed in addition to a page indicating the fact that the documents are falsified (Error Report) and a third mode in which all of the documents are not printed.
Therefore, when the print product based on the print data is constituted by plural printing objects (namely, pages or parts) and a specific page or part is falsified, the falsified specific page or part is also printed and included in the final print product, since the printing operation is implemented in either the first mode or the second mode mentioned in the above. Accordingly, there has been a problem that the user would erroneously recognize and handle the falsified specific page or part as a correct page or part. Further, when the abovementioned third mode is employed, there has arisen another problem that a certain processing that employs the documents concerned would piled up, since the correct pages or parts are also not printed.